The present invention relates to generally a method and device for coding video information and further compressing the coded video information, and more particularly a method and device for coding each interval (run-length) in which white or black elementary areas continue in succession in video information obtained by scanning a subject copy and further compressing the coded interval or run-length.
There has been recently devised and demonstrated a facsimile system in which the facsimile or video information is transmitted through a commercial telephone subscriber line with a low transmission speed from a transmitter to a receiver. When video information obtained by scanning a subject copy is transmitted through such a commercial telephone line, the transmission time is too long for practical purpose so that there have been proposed various methods for compressing the video information. One prior art method is such that an interval in which black or white elementary areas appear in succession, to be referred to as a "run-length" in this specification, is represented by a binary coded signal, and a discrimination bit "1" or "0" is inserted so that the binary coded signal representing a run-length of white elementary areas may be discriminated from that of a run-length of black elementary areas. However, a large number of discrimination bits which are not associated with the coding of run-lengths are contained in the transmitted signal as redundant bits so that the code compression ratio is low.
In view of the above, one of the objects of the present invention is to provide a method and device for weighting the discrimination bits "1"s and "0"s as in the case of the weighted bits in the coded run-length.
According to one embodiment of the present invention, a run-length of white or black elementary areas in video information is counted by a run-length counter. When a black elementary area changes to a white elementary area or vice versa, the content in the counter is read out in response to high-speed clock pulses and transferred into a transmitter buffer. In this case, a bit in each of specific bit positions in the buffer is replaced by a discrimination bit discriminating white or black elementary areas from black or white elementary areas.